Antifouling spark plug



Dec. 2, P O, STEWART I ANTIFOULING S PARK PLUG Filed Dec. 6: 11926 INVENTOR Paii'can ,Sie war.

' BY ATTORNEY Patented Dec. 2, 1930 Parar rereadY PATTERSON o. sT-Ewannor New Yoan, N. Y.

ANTIFoULrnG 'SPARK PLUG- Applicaton ledieceinber 6, 1926. Serial No.. 152,925.

i The present invention relates to spark plugs for internal combustion engines and more particularly to the structure and insulation of spark plug electrodes, whereby .fouling of the spark plug by carbon is minimized.

An important -feature of the invention is theprovision` of an annular insulating s urface of relatively narrow width separating a: grounded and an ungroundedr electrode, both appurtenant to the insulator, one of which hasa beveled edge that approaches the coacting electrode as it recedes from the face oi the insulator.` I

Another feature of theinvention is the provision of a series of subsidiary potential regulator gaps within the insulatlngbody of the spark plug.

Other and further features will be apparent to one skilled inthe art after a study of this specification taken in connection with the attached drawings, wherein Fig. 1 is a longitudinal central sectional view of the device; v

Fig. 2 is a sectional bottoml planview of the devi-ce on the 2 2 of F ig. 1, looking in the direction of the arrows of said line.

Referring to Fig. 1, the body or core 10 of thespark plug, which is of suitable insulating material, is provided at its upper portion with the central chamber 11 having at its bottom the bore 12 extending through the lower portion of the body and terminating at the lower end of the end portion 13a of reduced diameter below the tapered portion 13 of the body.

The body or core 10 is received in the shell 14 of the spark plug being held therein by the threaded metal gland 15, the body 10 having the enlarged portion 16, a packing ring 17 being disposed between the upper end of the portion 16 and the lower end of the gland 15 and a packing ring 18 being' disposedbetween the lower end of a shell 18a encasing said portion 13a and the ledge 19 at the lower end of the shell 14 for preventing loss of compression. The tapered end 13 of the body 10 is located in the chamber 2O formed by the lower portion of the shell 14.

The relatively thick disks 21 of conduc- 59 tive material are arranged in overlying and lowermost 22 of these disks resting on the `bottom ofthe chamber and having therein the threaded aperture 28, the disks 21, 22 being separated by the annular spacing members 24 of insulating material for thereby providingspark gaps between the disks.

rllhe domed instal cap 25 has secured thereto or formed as part thereof, the outwardly extending terminal stein 26 for connection to a supply of electricity, not shown, the stem 26 having the head 27 located under the domed portion of the cap. The cap 25 is secured over the upper end of the body 10, the concaved-convexed plate member 28 being loosely located in the space between the under side of the dome of the cap 25 and the uppermost of said disks 21 at the upperlend of the body 10, the concave side of this plate member 28 bearing against the head 27 of the stem 26 and the conveXed sideiofthe plate member bearing on the uppermost of the disks 21 and thereby retaining the disksV 21, 22 in the chamber 11.

The metal stein 29 is received in the bore 12, threadedly engaging at one of its ends in the aperture 23 oit' the disk 22 and having at its other end the sparking member or head 30, the .stein 29 and head 30 constituting the ungrounded electrode of the spark plug. A downwardly extending and inwardly tapering ring31 at the inner edge of a iiange 32at the lower end of said shell 18a constituting thegrounded electrode of the spark plug.

Y By referring to Fig. 1, it will benoted that the circular head 30 of the stem 29` has its bottom edge in substantially the Vsame horizontal plane asl theannularl end-prtion31 of the shell 18a, a gap being formed between the head 30 andthe annular end 31 of the Ashell 18a and of least width between the bottoni edge ofthe head 30 and the bottom edgeof the annular end portion 31, the intention being that sparks passing across said gap from the head 30 to the ring 31 shall pass from various parts of the circumferenl tial edge of the head 30 and not be confined to any particular part of the head 30.

rlhe klower portion 13a of thebody of the insulator extends into the interior of the shell 14 of the spark plug. This form is intended for use in engines having relatively high compression ratios.

The operation of this invention in use in a motor properly adjusted and not pumping oil is practically the same as any spark plug of conventional design, but for illustration, say, the motor starts to pump oil and the carburetor supplies a mixture slightly over-rich in fuel content, then at once the walls of the combustion chamber, includingr the portions ot the spark plug exposed to the explosion flame are subjected to carbonizing, the partially burnt excess lubricating oil acting as a binder and torming with the unconsumed portion of hydrocarbon in the mixture an amorphous carbon. T he carbon is thus forming on the insulator of a spark plug ot conventional design, acts as a high resistance leal-:between the electrodes and as the carbon coating gets thicker from continued operation, the resistance is lowered until the plug ceases to tire7 whereas with a spark plug designed as herein described the action is entirely ditierent, as will be described.

Referring to Fig. 1 et the annexed drawings it will be observed that the insulating space 31a between the grounded electrode 31 and the head 30 ot the ungrounded electrode is very narrow, being in tact only a few thousandths of an inch wider than the spark gap, as the carbon forms on this narrow insulating space suliiciently to lower its resistance to or below that of the spark gap the current will flow across at that point but this high resistance short being so narrow the current will heat the carbon to incandescence and it will therefore be dissipated or consumed, any leakage of current that might take place across the above mentioned high resistance short circuit is precluded by the series gaps 24 which hold the current in check until the voltage builds up to a high enough potential to produce a comparatively high ampere-flow. As can be seen, this structure also allows the insulating space 31a to be kept at a comparatively high temperature by the explosion flame tending to vaporize or dry any oil that might be deposited thereon.

The invention is presented as including also such modifications and changes as may property come within the following claims.

vWhat I claim and desire to protect by Letters Patent is:

1. In combination, a body of insulating material having an axial bore therethrough enlarged at its upper portion to form a chamber; a frequency changer comprising spaced metallic disks disposed in said chamber, a terminal stem connected to the topmost disk; an electrode stem in said bore connected to the lower disk and provided at its outer end with a disk shaped sparking electrode head formed with an annular sparking part spaced from said insulator; and an electrode co-op erating with said part to form a spark gap.

2. In combination, a cylindrical metallic shell; a body of insulating material therein having a downwardly tapered lower end and an axial bore therethrough enlarged at its upper portion to form a cylindrical chamber; a series of spaced thick metallic disks and insulating spacing ringV members alternated therewith superposed in said chamber, the lowest disk resting on the bottom of said chamber and provided with a central threaded aperture; a terminal stem connected to the topmost disk; a metal electrode stem in said bore of the body and having a reduced inner threaded `end engaged in said aperture of the disk and provided at its outer end with a sparking part; and anv electrode adjacent to said part and grounded on said shell.

3. In combination, a body of insulating material having an axial bore therethrough enlarged at its upper portion to form a chamber; a Afrequency changer comprising spaced metallic disks disposed in said chamber; said body having an annular groove around the upper end; a dome-topped metal cap secured on the upper end of said body and provided with an upper central opening and a lower inwardly pressed rib engaged in said groove; a downwardly concave-convened plate member in said cap and pressed against the topmost disk; a threaded terminal stem in said opening and having a head disposed between said plate member and dome top an electrode stem in said bore connected to the lower disk and provided at its outer end with a sparking part; and an electrode co-operating with said part to form a spark gap.

Signed at New York in the county of New York and State of New York this 4th day of December, A. D. 1926.

PATTERSON O. STEVART. 

